You can reach the bottom of a paragraph and realise that nothing came with you. Your eyes did the whole job: they kept the line, turned at the margin, would probably have caught a typo. So you go back to the top, and halfway down the second pass you notice you’re thinking about the email you haven’t answered, and you go back again. By the third time it reads easily, and it feels as if the paragraph has relented, though not a word of it has changed. The same thing happens out loud. A parent can read a bedtime story with all the voices, pausing in all the right places, while planning tomorrow’s lunches, and the child gets the whole story. It’s an odd kind of proof that a paragraph can be delivered perfectly by someone it never reached.